1. Field of the Invention
The invention relates to a communicating method, a transmitting apparatus, and a receiving apparatus, in which a unidirectional communication medium such as a digital broadcasting is made to look like a bidirectional communication medium, thereby making it possible to perform a path control in which a bidirectional communication medium is used as a prerequisite.
2. Description of the Related Art
For example, communication using a communication satellite or a partial CATV as a medium is a unidirectional communication and an application, a communication protocol, and the like on a satellite broadcasting have been designed in consideration of a unidirectional topology. In recent years, a method of sending a packet of an IP (Internet Protocol) to a satellite network has been tried in association with the spread of the Internet.
The application on the Internet, however, has been usually developed in consideration of only the bidirectional communication medium such as Ethernet, FDDI (Fiber Distributed Interface: optical LAN of 100 Mbps), or the like. Therefore, under an environment using the unidirectional communication medium like a satellite broadcasting, if the application used on the Internet is used, such a trouble that the communication cannot be properly performed occurs.
When a router is connected to a satellite line, since a path control program operating at present on the router has been designed on the assumption that the line to which the router is connected is a bidirectional communication medium, a problem occurs. A path control packet transmitted by a certain router has to directly arrive at an interface of an adjacent router connected to the same segment as that of an interface to which such a router generated the packet. Since the satellite line is unidirectional, however, although a packet can be sent from the transmitting side to the receiving side via the satellite line, a packet cannot be transmitted from the receiving side to the transmitting side via the satellite line. Since the router cannot bidirectionally communicate via the satellite line, the communication using the satellite line cannot be correctly performed. In the case where the unidirectional communication medium like a satellite line is used as mentioned above, a problem occurs in the communication of the router or node on which the path control program operates.